Bibian van der Voorn

127 EARLY LIFE GROWTH ON CORTISOL AFTER PREMATURITY investigated using univariable regression, with birth weight SDS as independent, continuous factor. Second, the association between birth weight ≤–2SDS and cortisol was investigated, with birth weight SDS as independent, dichotomous factor. Third, the association between SGA-status and cortisol was investigated, with SGA-status as independent, dichotomous factor. Fourth, infants were classified into 4 groups according to birth weight SDS and growth from birth to 6 mo. corrected age (see also section 2.1 ): AGA GR– (1), AGA GR+ (2), SGA CUG– (3) and SGA CUG+ (4). Subsequently, the influence of growth pattern on cortisol was investigated, with the groups as independent, categorical factor and AGA GR– as reference category. Fifth, in order to test the stability of our data, all analyses were repeated, adjusted for perinatal or other characteristics that were significantly different between AGA and SGA subjects, one by one ( Table 2 ). TABLE 1. Baseline characteristics of all subjects, and STEP-2 participants, STEP-2 non-participants and excluded subjects. All subjects STEP-2 Participants STEP-2 Non-participants STEP-2 Excluded subjects P-value a n 152 79 52 21 Perinatal characteristics Male 78 (51) 40 (51) 26 (50) 12 (57) NS Gestational age wks 30 [30 to 31] range 25 to 33 31 [29 to 32] 30 [30 to 31] 31 [30 to 32] NS Birth weight g 1339 ± 29 range 710 to 2065 1314 ± 304 1350 ± 290 1404 ± 265 NS SDS –0.3 ± 1.0 range –2.8 to 1.9 –0.4 ± 1.0 –0.3 ± 0.9 –0.2 ± 1.2 NS Birth length cm 38 ± 3.0 38 ± 3.1 38 ± 3.0 38 ± 2.9 NS SDS –0.9 ± 1.2 range –3.9 to 2.0 –0.8 ± 1.3 –1.1 ± 1.1 1.0 ± 1.3 NS SGA 35 (23) 17 (22) 13 (28) 5 (24) NS Birth head circumference cm 27.7 ± 1.9 27.6 ± 1.9 27.7 ± 1.9 28.0 ± 1.8 NS SDS –0.2 ± 1.1 –0.2 ± 1.1 –0.3 ± 1.0 –0.21 ± 1.3 NS NTISS 21.4 ± 7.6 21.9 ± 7.8 21.4 ± 7.1 19.8 ± 8.0 NS Weight 6 mo. corrected age kg 7.3 ± 1.1 7.2 ± 1.0 7.4 ± 1.0 7.6 ± 1.4 NS SDS –0.4 ± 1.2 –0.5 ± 1.2 –0.3 ± 1.2 –0.3 ± 1.7 NS Length 6 mo. corrected age cm 66.4 ± 2.9 66.4 ± 2.8 66.5 ± 2.9 66.4 ± 3.4 NS SDS –0.3 ± 1.1 –0.4 ± 1.1 –0.3 ± 1.1 –0.5 ± 1.4 NS Demographics Parents that finished higher education neither 77 (52) 41 (53) 23 (45) 13 (62) NS one 32 (22) 15 (19) 13 (26) 4 (21) both 39 (26) 22 (28) 15 (29) 2 (11) ≥1 parent non-Caucasian 43 (28) 17 (22) 13 (25) 13 (62) <0.01 Data are expressed as mean ± SD, median [IQR], or n (%). Abbreviations: NS, non-significant; NTISS, neonatal therapeutic intervention scoring system; SDS, SD-score; SGA, small for gestational age (birth weight and/or birth length ≤–2SDS) a STEP-2 participants, STEP-2 non-participants and excluded subjects were compared using one-way ANOVA, Chi-square or Kruskal-Wallis tests, as appropriate. SALIVARY CORTISOL AT AGE 8 YEARS Data were examined for outliers. Levels at awakening that were 10 times higher than 15 min. after awakening, and levels in the evening that were 10 times higher than the cohort mean, were excluded.